Waste-to-energy technologies: Integrating anaerobic digestion, microbial electrolysis cells, hydrodynamic cavitation, and electrocoagulation

This study explores a novel integration of electro-physicochemical technologies to generate energy and treat water from combined food waste (FW) and blackwater (FW-BW), with BW containing waste activated sludge with simulated flush water. The FW-BW substrate was gravity-separated and pretreated with hydrodynamic cavitation (HDC). Solids from gravity separation were used for energy generation via anaerobic digestion (AD) alone or integrated with microbial electrolysis cells (AD-MEC). HDC pretreatment had 51.6% more CH₄ production in 5 days (266 mL CH₄/g VS) and 63% more in 30 days compared to AD without HDC. The CH₄ production after 5 days of digestion with HDC pretreatment (266 mL CH₄/g VS) was similar to the amount produced without HDC over 30 days (263 mL CH₄/g VS). Using MEC increased CH₄ production by 12.7% compared to AD-only. The liquids from gravity separation were treated with electrocoagulation (EC) at 15 V (90 min), which removed 96.2% of the chemical oxygen demand (COD) and 100% of the total suspended solids. The pilot scale design indicates that the AD-MEC and EC units would generate 1.4 times more energy than energy consumed through applying these novel technologies. These findings demonstration the applications of four technologies (HDC, AD, MEC, and EC) in an energy-efficient waste management approach, producing bioenergy and cleaner water for low-tier use, especially in areas lacking traditional waste treatment options.